For the past 90 years, archaeologists have been scouring Pembrokeshire's Preseli Hills in search of clues that could shed light on where the bluestones used to build the famous monument came from. But it turns out that the rocks may have originated from another hill — one that's just a mile away.

Just where the massive rocks came from, and how they were transported from so far away, is a mystery that still baffles archaeologists. Back in 1923, geologist Herbert Henry Thomas proposed that the distinctive spotted dolerites were hauled from Wales to Wiltshire some 5,000 years ago via land and sea — a distance of 150 miles (240 km). A more recent theory suggests they were carried east on an ice-age glacier about 20,000 years ago.

For centuries, the iconic boulders of Stonehenge have puzzled researchers the word over — for what…
Read more Read more

Eager to solve this mystery, archaeologists have been trying to locate the exact outcrop of dolerite in Wales. For the past 90 yeas, they figured it was at Carn Meini, and that's where they've been digging.

Dr Bevins's team are able to say so categorically that they have discovered the source of the spotted dolerites thanks to a range of laser mass spectrometry techniques which analyse both the chemical composition of the rock and the microbiology present when it was formed.

He says that the chance of them having originated anywhere other than Carn Goedog is "statistically-speaking, infinitesimally small".

And while he is the first to admit that this discovery on its own gets us no closer to solving the riddle, he believes a definitive answer will come eventually.

"I've been studying the bluestones for over 30 years now, and I'm no closer to finding an answer which convinces me either way. But the one thing which I am increasingly sure of is that each piece of the puzzle we find brings us another step closer to the truth.

Archaeologists, who have spent decades digging at the apparently wrong location, will soon be moving to the new site.

"I don't expect to get Christmas cards from the archaeologists who have been excavating at the wrong place all these years," noted Bevins in a statement. His findings are set to be published in an upcoming edition of the Journal of Archaeological Science.